Macromonomers have been the subject of active investigation over the last several years, a macromonomer being a polymer or oligomer that contains a polymerizable functional group. Graft copolymer with a well-defined branch length and number of branches can be synthesized through the use of a macromonomer as the branching element in the graft copolymer. General reviews in this area are available, for example, Makurom onomaa no Kagaku to Kogyo [The Chemistry and Technology of Macromonomers], edited by Y. Yamashita, IPC (1989); Y. Kawakami, Kobunshi, volume 37, p. 264 (1988); and Y. Chujo, Kobunshi, volume 39, p. 452 (1990).
Most of the macromonomers known to date have the vinylphenyl group, acryloyl group, or methacryloyl group as their terminal polymerizable group, and these are used mainly for chain-growth polymerization. However, macromonomers for step-growth polymerization have been reported: these contain a terminal diol, dicarboxylic acid, dicarboxylic acid ester, diamine, phenol, and so forth. See, for example, Tezuka et al., Polymer, volume 30, p. 553 (1989); Tezuka et al., Macromolecules, volume 24, p. 122 (1991); Kawakami et al., Polym. Bull., volume 25, p. 521 (1991); Okawa et al., Japanese Patent Application Laid Open Hei 1-132634; Nagase et al., Makromol. Chem. Rapid Commun., volume 11, p. 185 (1990); Nagase et al., Japanese Patent Application Laid Open Number Hei 1-185327; and K. M. Snow, et al., Canadian Patent 2,025,289.
However, neither organopolysiloxane carrying phthaloyl halide as its polymerizable group nor a process for the preparation of such an organopolysiloxane have been reported up to now. Such a polysiloxane would be useful for the synthesis of novel polymers having organopolysiloxane side chains and a main chain of polyester, polyarylate, polyamide, polybenzobisoxazole, and so forth. Furthermore, aromatic polymers, such as aromatic polyesters, aromatic polyamides (aramides), and aromatic polyimides, have begun to occupy an important position as high-performance polymers due to their high mechanical strength, heat resistance and solvent resistance, (see, for example, High-Performance Aromatic Polymers (Koseino Hokozoku-kei Kobunshi Zairyo), edited by the Society of Polymer Science, Japan, Maruzen (1990)). However, these rigid linear polymers have lower solvent solubilities and higher melting points than conventional flexible polymers and thus present greater problems from the standpoint of processing. As a result, the industrial development and utilization of such polymers has only just begun in recent years.
The introduction of flexible polymers as side chains has been proposed as one method for improving the solubility and lowering the melting points of such rigid linear aromatic polymers (see for example M. Ballauff, Angew. Chem. Int. Ed. Engl., volume 28, page 253 (1989)). The following, for example, have been reported for this purpose: aromatic polyesters carrying alkyl or alkyloxy side chains and aromatic polyesters into which alkyl chains have been introduced by ester bonding (see R. W. Lenz et al., Eur. Polym. J., volume 19, page 1043 (1983); M. Ballauff, Makromol. Chem., Rapid Commun., volume 7, page 407 (1986); B. R. Harkness et al., Macromolecules, volume 24, page 6759 (1991), etc.), polystyrene-grafted aromatic polyesters (see T. Heitz et al., Makromol. Chem., volume 190, page 3295 (1989)), and aromatic polyimides carrying alkyloxy side chains (see M. Ballauff et al., Makromol. Chem., volume 188, page 2865 (1987)). Examples have also been reported of the introduction of polysiloxane side chains onto semi-flexible linear aromatic polyimides for the purpose of obtaining separation membranes (see Nagase et al., Makromol. Chem., volume 193, page 1509 (1992).
However, organopolysiloxane-grafted polybenzobisoxazoles and their copolymers have been unknown up to now. In addition to the above-mentioned improvement in solubility, and so forth, novel characteristics which combine the properties of polybenzobisoxazoles and polysiloxanes may be expected from such organopolysiloxane-grafted polybenzobisoxazoles.